    /* 
     * A JavaScript implementation of the RSA Data Security, Inc. MD5 Message 
     * Digest Algorithm, as defined in RFC 1321. 
     * Version 1.1 Copyright (C) Paul Johnston 1999 - 2002. 
     * Code also contributed by Greg Holt 
     * See http://pajhome.org.uk/site/legal.html for details. 
     */

    /* 
     * Add integers, wrapping at 2^32. This uses 16-bit operations internally 
     * to work around bugs in some JS interpreters. 
     */
    function safe_add(x, y) {
    	var lsw = (x & 0xFFFF) + (y & 0xFFFF)
    	var msw = (x >> 16) + (y >> 16) + (lsw >> 16)
    	return (msw << 16) | (lsw & 0xFFFF)
    }

    /* 
     * Bitwise rotate a 32-bit number to the left. 
     */
    function rol(num, cnt) {
    	return (num << cnt) | (num >>> (32 - cnt))
    }

    /* 
     * These functions implement the four basic operations the algorithm uses. 
     */
    function cmn(q, a, b, x, s, t) {
    	return safe_add(rol(safe_add(safe_add(a, q), safe_add(x, t)), s), b)
    }

    function ff(a, b, c, d, x, s, t) {
    	return cmn((b & c) | ((~b) & d), a, b, x, s, t)
    }

    function gg(a, b, c, d, x, s, t) {
    	return cmn((b & d) | (c & (~d)), a, b, x, s, t)
    }

    function hh(a, b, c, d, x, s, t) {
    	return cmn(b ^ c ^ d, a, b, x, s, t)
    }

    function ii(a, b, c, d, x, s, t) {
    	return cmn(c ^ (b | (~d)), a, b, x, s, t)
    }

    /* 
     * Calculate the MD5 of an array of little-endian words, producing an array 
     * of little-endian words. 
     */
    function coreMD5(x) {
    	var a = 1732584193
    	var b = -271733879
    	var c = -1732584194
    	var d = 271733878

    	for (var i = 0; i < x.length; i += 16) {
    		var olda = a
    		var oldb = b
    		var oldc = c
    		var oldd = d

    		a = ff(a, b, c, d, x[i + 0], 7, -680876936)
    		d = ff(d, a, b, c, x[i + 1], 12, -389564586)
    		c = ff(c, d, a, b, x[i + 2], 17, 606105819)
    		b = ff(b, c, d, a, x[i + 3], 22, -1044525330)
    		a = ff(a, b, c, d, x[i + 4], 7, -176418897)
    		d = ff(d, a, b, c, x[i + 5], 12, 1200080426)
    		c = ff(c, d, a, b, x[i + 6], 17, -1473231341)
    		b = ff(b, c, d, a, x[i + 7], 22, -45705983)
    		a = ff(a, b, c, d, x[i + 8], 7, 1770035416)
    		d = ff(d, a, b, c, x[i + 9], 12, -1958414417)
    		c = ff(c, d, a, b, x[i + 10], 17, -42063)
    		b = ff(b, c, d, a, x[i + 11], 22, -1990404162)
    		a = ff(a, b, c, d, x[i + 12], 7, 1804603682)
    		d = ff(d, a, b, c, x[i + 13], 12, -40341101)
    		c = ff(c, d, a, b, x[i + 14], 17, -1502002290)
    		b = ff(b, c, d, a, x[i + 15], 22, 1236535329)

    		a = gg(a, b, c, d, x[i + 1], 5, -165796510)
    		d = gg(d, a, b, c, x[i + 6], 9, -1069501632)
    		c = gg(c, d, a, b, x[i + 11], 14, 643717713)
    		b = gg(b, c, d, a, x[i + 0], 20, -373897302)
    		a = gg(a, b, c, d, x[i + 5], 5, -701558691)
    		d = gg(d, a, b, c, x[i + 10], 9, 38016083)
    		c = gg(c, d, a, b, x[i + 15], 14, -660478335)
    		b = gg(b, c, d, a, x[i + 4], 20, -405537848)
    		a = gg(a, b, c, d, x[i + 9], 5, 568446438)
    		d = gg(d, a, b, c, x[i + 14], 9, -1019803690)
    		c = gg(c, d, a, b, x[i + 3], 14, -187363961)
    		b = gg(b, c, d, a, x[i + 8], 20, 1163531501)
    		a = gg(a, b, c, d, x[i + 13], 5, -1444681467)
    		d = gg(d, a, b, c, x[i + 2], 9, -51403784)
    		c = gg(c, d, a, b, x[i + 7], 14, 1735328473)
    		b = gg(b, c, d, a, x[i + 12], 20, -1926607734)

    		a = hh(a, b, c, d, x[i + 5], 4, -378558)
    		d = hh(d, a, b, c, x[i + 8], 11, -2022574463)
    		c = hh(c, d, a, b, x[i + 11], 16, 1839030562)
    		b = hh(b, c, d, a, x[i + 14], 23, -35309556)
    		a = hh(a, b, c, d, x[i + 1], 4, -1530992060)
    		d = hh(d, a, b, c, x[i + 4], 11, 1272893353)
    		c = hh(c, d, a, b, x[i + 7], 16, -155497632)
    		b = hh(b, c, d, a, x[i + 10], 23, -1094730640)
    		a = hh(a, b, c, d, x[i + 13], 4, 681279174)
    		d = hh(d, a, b, c, x[i + 0], 11, -358537222)
    		c = hh(c, d, a, b, x[i + 3], 16, -722521979)
    		b = hh(b, c, d, a, x[i + 6], 23, 76029189)
    		a = hh(a, b, c, d, x[i + 9], 4, -640364487)
    		d = hh(d, a, b, c, x[i + 12], 11, -421815835)
    		c = hh(c, d, a, b, x[i + 15], 16, 530742520)
    		b = hh(b, c, d, a, x[i + 2], 23, -995338651)

    		a = ii(a, b, c, d, x[i + 0], 6, -198630844)
    		d = ii(d, a, b, c, x[i + 7], 10, 1126891415)
    		c = ii(c, d, a, b, x[i + 14], 15, -1416354905)
    		b = ii(b, c, d, a, x[i + 5], 21, -57434055)
    		a = ii(a, b, c, d, x[i + 12], 6, 1700485571)
    		d = ii(d, a, b, c, x[i + 3], 10, -1894986606)
    		c = ii(c, d, a, b, x[i + 10], 15, -1051523)
    		b = ii(b, c, d, a, x[i + 1], 21, -2054922799)
    		a = ii(a, b, c, d, x[i + 8], 6, 1873313359)
    		d = ii(d, a, b, c, x[i + 15], 10, -30611744)
    		c = ii(c, d, a, b, x[i + 6], 15, -1560198380)
    		b = ii(b, c, d, a, x[i + 13], 21, 1309151649)
    		a = ii(a, b, c, d, x[i + 4], 6, -145523070)
    		d = ii(d, a, b, c, x[i + 11], 10, -1120210379)
    		c = ii(c, d, a, b, x[i + 2], 15, 718787259)
    		b = ii(b, c, d, a, x[i + 9], 21, -343485551)

    		a = safe_add(a, olda)
    		b = safe_add(b, oldb)
    		c = safe_add(c, oldc)
    		d = safe_add(d, oldd)
    	}
    	return [a, b, c, d]
    }

    /* 
     * Convert an array of little-endian words to a hex string. 
     */
    function binl2hex(binarray) {
    	var hex_tab = "0123456789abcdef"
    	var str = ""
    	for (var i = 0; i < binarray.length * 4; i++) {
    		str += hex_tab.charAt((binarray[i >> 2] >> ((i % 4) * 8 + 4)) & 0xF) +
    			hex_tab.charAt((binarray[i >> 2] >> ((i % 4) * 8)) & 0xF)
    	}
    	return str
    }

    /* 
     * Convert an array of little-endian words to a base64 encoded string. 
     */
    function binl2b64(binarray) {
    	var tab = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
    	var str = ""
    	for (var i = 0; i < binarray.length * 32; i += 6) {
    		str += tab.charAt(((binarray[i >> 5] << (i % 32)) & 0x3F) |
    			((binarray[i >> 5 + 1] >> (32 - i % 32)) & 0x3F))
    	}
    	return str
    }

    /* 
     * Convert an 8-bit character string to a sequence of 16-word blocks, stored 
     * as an array, and append appropriate padding for MD4/5 calculation. 
     * If any of the characters are >255, the high byte is silently ignored. 
     */
    function str2binl(str) {
    	var nblk = ((str.length + 8) >> 6) + 1 // number of 16-word blocks  
    	var blks = new Array(nblk * 16)
    	for (var i = 0; i < nblk * 16; i++) blks[i] = 0
    	for (var i = 0; i < str.length; i++)
    		blks[i >> 2] |= (str.charCodeAt(i) & 0xFF) << ((i % 4) * 8)
    	blks[i >> 2] |= 0x80 << ((i % 4) * 8)
    	blks[nblk * 16 - 2] = str.length * 8
    	return blks
    }

    /* 
     * Convert a wide-character string to a sequence of 16-word blocks, stored as 
     * an array, and append appropriate padding for MD4/5 calculation. 
     */
    function strw2binl(str) {
    	var nblk = ((str.length + 4) >> 5) + 1 // number of 16-word blocks  
    	var blks = new Array(nblk * 16)
    	for (var i = 0; i < nblk * 16; i++) blks[i] = 0
    	for (var i = 0; i < str.length; i++)
    		blks[i >> 1] |= str.charCodeAt(i) << ((i % 2) * 16)
    	blks[i >> 1] |= 0x80 << ((i % 2) * 16)
    	blks[nblk * 16 - 2] = str.length * 16
    	return blks
    }

    /* 
     * External interface 
     */
    function hexMD5(str) {
    	return binl2hex(coreMD5(str2binl(str)))
    }

    function hexMD5w(str) {
    	return binl2hex(coreMD5(strw2binl(str)))
    }

    function b64MD5(str) {
    	return binl2b64(coreMD5(str2binl(str)))
    }

    function b64MD5w(str) {
    	return binl2b64(coreMD5(strw2binl(str)))
    }
    /* Backward compatibility */
    function calcMD5(str) {
    	return binl2hex(coreMD5(str2binl(str)))
    }
    module.exports = {
    	hexMD5: hexMD5
    }